[Devel] Re: [PATCH 3/5] cr: add generic LSM c/r support

[Casey Schaufler]

Stephen Smalley wrote:
> On Sun, 2009-08-30 at 12:03 -0700, Casey Schaufler wrote:
>   
>> Serge E. Hallyn wrote:
>>     
>>> Quoting Casey Schaufler (casey at schaufler-ca.com):
>>>   
>>>       
>>>> Serge E. Hallyn wrote:
>>>>     
>>>>         
>>>>> Quoting Casey Schaufler (casey at schaufler-ca.com):
>>>>>       
>>>>>           
>>>>>> But each can be expressed as a context, can't it?
>>>>>>     
>>>>>>         
>>>>>>             
>>>>> A set of contexts (root_u:root_r:root_t:::system_u:system_r\
>>>>> :system_t::...).
>>>>>
>>>>> There would be a problem if it were stored as a more
>>>>> structured type, and if the ->restore handler wanted to
>>>>> re-create an actual task_security_struct, ipc_security_struct,
>>>>> etc.  So the last paragraph in the patch intro was just trying to
>>>>> explain why the intermediate layer, storing a generic string on
>>>>> the c/r object hash, needs to be there.  The thing that is
>>>>> not possible is to place the actual void *security or a struct
>>>>> task_security_struct on the objhash.
>>>>>   
>>>>>       
>>>>>           
>>>> Right. Now why do you need a set of contexts?
>>>>     
>>>>         
>>> Because for SELinux, for instance, when checkpointing a security
>>> context for a task, we want to checkpoint the actual context,
>>> the fscreate context, the sockcreate context, keycreate context,
>>> and the task create (exec_create) context.
>>>   
>>>       
>> My. That is quite a lot of contexts to keep track of.
>>     
>
> Doesn't Smack also have at least one case where it supports multiple
> distinct contexts for different purposes on a single object (e.g.
> sockets)?
>   

Smack does support associating labels with incoming and/or
outgoing packets from a particular socket. I haven't looked
carefully at how the checkpoint/restart scheme is handling
sockets in general, so I couldn't say if its going to get the
rest of it right, either. In any case, that's something that
is strictly in the realm of privileged processes for which
checkpoint/restart is going to be one hairy potato.

Processes that use this mechanism will be quite rare. The
Smack port multiplexer (smackpolyport) that I'll be talking
about in Portland and a small set of security enforcing
applications should be about it.

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